1. Field of Invention
The invention relates to, in general a method of controlling a vehicle equipped with an internal-combustion engine and, in particular, such a method using a “stop and start” system.
2. Description of Related Art
An internal-combustion engine includes a number of cylinders (normally, four arranged in line) equipped with respective pistons connected to an engine crankshaft by connecting rods. The shaft of an electric-starter motor powered by the vehicle's battery is also mechanically connected to the engine crankshaft of the internal-combustion engine. To start the internal-combustion engine, the electric motor drives the engine crankshaft into rotation from a starting position in which the engine crankshaft is stationary. As soon as the engine crankshaft starts to turn, fuel is directly or indirectly injected into the cylinders to try to achieve initial firing in the shortest possible time and, consequently, enable the internal-combustion engine to become self-sustaining.
The “stop and start” system stops the internal-combustion engine when the vehicle is stationary or about to stop [typically, for traffic-related motives (such as a red traffic light) or crossroads without right of way] and restarts the internal-combustion engine as soon as the driver operates the clutch pedal.
Certain problems arise in vehicles equipped with an internal-combustion engine with a “stop and start” system and a manual gearbox.
As the “stop and start” system is implemented by the engine-control unit (that is to say, it is set op to enable and disable this system, which stops the internal-combustion engine when the vehicle is stationary or about to stop and restarts it as soon as the driver operates the clutch pedal), it is extremely important that the engine-control unit can accurately and precisely identity the “neutral gear” condition.
For example, EP1104859 discloses a method of controlling the transmission of a vehicle, which includes the steps of providing a pair of position sensors and using the signals coming from both the position sensors to determine the “neutral gear” condition.
EP718142 discloses a “gearshift control” system (in particular, for tractors or other earth-moving machines) that includes in a preliminary “setting up” phase the step of providing a position sensor that is set to read the position of the gearshift actuator piston. This method includes furthermore the steps of learning by the position sensor a first and second end value, calculating a first threshold value through the algebraic sum of the first end value and a correction margin, calculating a second threshold value through the algebraic difference between the second end value and correction margin, and determining a value range (which corresponds to the “neutral gear” condition) as a function of the mean value of the first threshold value, the second threshold value, and a constant value.
JP2008302821 discloses a method of controlling the gearshift of a vehicle, which includes in a preliminary “setting up” phase the step of arranging close to the driver-operated gear-selection lever a sensor that is set to read when in use the position of the gear-selection lever. This method includes furthermore the step of learning the value read by the sensor, which corresponds to the “neutral gear” condition, in an initial learning step.
JP2010060125 discloses a method of learning the reference position of a driver-operated gear-selection lever as a function of the comparison between two signals coming from a pair of sensors in successive operating cycles.
U.S. Pat. No. 6,393,928 discloses a system for controlling the gearshift of a vehicle by a pair of sensors. The method includes, at first, the step of learning the values read by the sensors (which correspond to the “neutral gear” condition) and, subsequently, the step of engaging the other even and odd gears.
U.S. Pat. No. 5,875,670 discloses an apparatus for controlling the gearshift of a vehicle equipped with a pair of position sensors. The method includes the steps of determining in a preliminary “setting up” phase a set of tolerance values and learning the values read by the sensors, which correspond to the “neutral gear” condition that is in a substantially central position. During normal vehicle running, the “even or odd gear” condition is determined as a function of the comparison of the signals coming from the pair of position sensors with the values corresponding to the “neutral gear” condition and set of tolerance values.
U.S. Pat. No. 5,660,079 discloses a system for controlling the transmission of a vehicle equipped with a sensor arranged close to the shift lever. The method includes the step of learning the values read by the sensor to determine the “forward and reverse gear” conditions and “neutral, gear” condition. In particular, the method includes the step of learning the value react by the sensor, which corresponds to the “neutral gear” condition in an initial learning step to allow the subsequent learning of the “forward and reverse gear” conditions.
U.S. Patent Application Publication 201109881 discloses a system for controlling a vehicle provided with a pair of sensors that are both arranged close to the shift lever. The method includes the steps of determining in a preliminary step a value range associated with each possible gear condition and comparing in use each value range with the signals coming from the pair of sensors to determine the gear condition.
The methods described above, though, do not guarantee an accurate and precise identification of a “neutral gear” condition that, above all, is reliable in time (even in a ease of fault of some components). This can cause a failure to stop and/or an undesired restarting of the vehicle's engine with the “stop and start” system.
The object of the invention is to provide a method of controlling a vehicle equipped with an internal-combustion engine with a “stop and stall” system, which method permits the drawbacks of the related art to be overcome while being simple and inexpensive to implement.